I already own this display (the LG UltraFine 4K) and I'm thinking of additionally purchasing the 5K display for use with my 2018 13" MacBook Pro with Touch Bar. Can the 4K display be connected to one of the output USB-C ports on the 5K display, thereby daisy-chaining it? I would prefer not to connect the two displays directly to my laptop, if possible.

The LG UltraFine 5K Display is a Thunderbolt 3 display which uses both DisplayPort connections of the computer's Thunderbolt controller. The Thunderbolt controller sends both DisplayPort signals to the Thunderbolt controller of the LG UltraFine 5K over the Thunderbolt cable. The Thunderbolt controller in the LG UltraFine 5K converts both Thunderbolt DisplayPort streams back into DisplayPort to be used by each half of the display (the left and right sides) to support 5K resolution.

That is also the reason why the LG 5K display does not have a second Thunderbolt 3 port - because it is required for one of the DisplayPort signals for one half of the display. The other DisplayPort signal comes out of a DisplayPort connection of the Thunderbolt controller of the display (think of a Thunderbolt 3 dock where you can connect one display to the second Thunderbolt 3 port of the dock, and another display to a DisplayPort output of the dock).

The Thunderbolt controller of the computer does not have a third DisplayPort connection, and since the LG 5K uses two DisplayPort connections (over Thunderbolt), an LG 4K display cannot be daisy chained to the LG 5K display.

Also, since a Thunderbolt controller only has two DisplayPort connections, if you connect a LG 5K to one side of the MacBook Pro, then a second display must be connected to the other side of the MacBook Pro (there's one Thunderbolt controller per side of the MacBook Pro). One 5K or two 4K per side of the MacBook Pro can be connected.

The USB-C ports of the LG UltraFine 5K only support USB. They do not support DisplayPort because there is no other DisplayPort signal on the Thunderbolt cable that can be used and the display has no other DisplayPort inputs.

It might be possible to use a USB to DisplayPort converter (research devices that use DisplayLink, find examples at the DisplayLink or plugable websites) but they don't perform like real displays and may have issues in macOS.

Yes. I use two on my 2017 MacBook Pro 15inch. One in portrait and the other in landscape. You just need a different mount; the mount provided only does landscape so you will need to VESA mount the display.

The general consensus of people I've talked to recommend against long-term operation of a MacBook Pro with a "less than stock" power supply. That is, people say you can damage a MacBook Pro 15 using the power supply for a MacBook Air, for example.
So can you just plug the USB-C connector from this display into the new MacBook Pro 15 as a single-plug "dock", or do you need to plug in the MacBook Pro's power supply as well?

I use it with a 15" MacBook Pro and it charges fine. The only difference is in the time it takes to charge the MacBook if it's discharged when connecting it. There's no reason at all you can't use the lower wattage without damaging your battery. Exactly the same as you can use lower wattage adapters for iPads for example, it just charges slower.

I purchased the new Blackmagic eGPU which has two Thunderbolt 3 ports and one HDMI 2.0 port. One of the Thunderbolt 3 ports runs to my MacBook Pro, and the other Thunderbolt 3 port should be able to run to the LG display no problem.

Where the question lies is is it possible to connect a USB C display such as the LG UltraFine 4K to an HDMI 2.0 output using adapters or a USB-C to HDMI cable?

Hi I had this problem, the solution is to purchase a certified thunderbolt 3 (USB-C) cable, like belkin on the Apple Store £22 at the moment, which is what I did and the monitor works perfectly, also regardless of what others say, the Macbook pro 15" seems to charge from the monitor no problem, hope this helps

According to the document HT207447 "Use the LG UltraFine 4K Display with your MacBook or MacBook Pro" on Apple's support website, it will not work with Macs that use Thunderbolt 2.

Maybe it will accept a DisplayPort signal? Try using a USB-C to mini DisplayPort cable to find out.

The Apple Thunderbolt 3 to Thunderbolt 2 adapter is for Thunderbolt devices only. It does not pass DisplayPort signals.

The LG UltraFine 5K Display is a Thunderbolt display but will only work at 4K @ 60 Hz when using a Thunderbolt 2 port of the Mac Pro 2013. Read the document HT207448 "Use the LG UltraFine 5K Display with your Mac" for more information about that.

Hi all, I'm wondering if this display is compatible with the previous generation of Retina MacBook Pros? More specifically, my 15" Mid 2014 Retina MacBook Pro (2.8GHz QC i7, 16GB RAM, 1TB SSD, GT 750M 2GB)? I know this display only has USB-C inputs, but if I bought one of Belkin's USB-A to USB-C cables, would it work? It is from my understanding that USB-C is really just a smaller, reversible version of USB 3.1. Thanks again, -Alex

As far as I can tell, it is not. I have a mid-2015 15" macbook pro with retina display, 2.8 GHz Intel Core i7 processor, 16 gb of ram and Intel Iris Pro 1536 MB graphics card.

I've tried it with TB 3 to TB 2 convertor and an HDMI cable, a USB-C to mini DisplayPort convertor and mini DisplayPort cable, and USB-C to 4k HDMI convertor with HDMI cable / port as well, all with no luck. The mac does connect to an old TV using the HDMI cord, so I don't think it's an issue with the mac. The plan from here is to call LG support and find out if there's ANYTHING I can do that will allow me to use the monitor with the mac. Otherwise, I sure hope they'll take it back at apple, since my company bought it and I've already discarded the box.